The other ratio of Revillout and Hultsch, 320 hons = cubit cubed, is certainly approximate.
By the theory of maris 1/5 of 20.6 cubed is 1755; by maris = Assyrian talent, 1850, in place of 1850 or 1980 stated above; hence the more likely theory of weight, rather than cubit, connexion is nearer to the facts.
Beside the equivalence of the hon to 5 utens weight of water, the mathematical papyrus (35) gives 5 besha = (2/3)cubic cubit (Revillout's interpretation of this as 1 cubit cubed is impossible geometrically; see Rev. Eg., 1881, for data); this is very concordant, but it is very unlikely for 3 to be introduced in an Egyptian derivation, and probably therefore only a working equivalent.
In.; their log-measure, holding six hen's eggs, shows it to be over rather than under this amount; but their reckoning of bath = a half cubit cubed is but approximate; by 21.5 it is 1240, by 25.1 it is 1990 cubic in.